1. Field of the Invention
The present invention is directed to low surface energy polyisocyanates which contain allophanate groups and fluorine, to blends of these polyisocyanates with other polyisocyanates which do not contain fluorine and to the use of either of these polyisocyanates in one- or two-component coating compositions.
2. Description of the Prior Art
Polyurethane coating compositions containing a polyisocyanate component, in either blocked or unblocked form and an isocyanate reactive component, generally a high molecular weight polyol, are well known. Although coatings prepared from these compositions possess many valuable properties, one property, in particular, which needs to be improved is the surface quality. It can be difficult to formulate coating compositions to obtain a coating having a smooth surface as opposed to one containing surface defects such as craters, etc.
It is believed that these difficulties are related to the high surface tension of the two-component coating compositions. Another problem caused by the high surface tension is the difficulty in cleaning the coatings. Regardless of their potential application area, there is a high likelihood that the coatings will be subjected to stains, graffiti, etc.
Accordingly, it is an object of the present invention to provide coating compositions which have reduced surface tension and, thus, are suitable for the production of coatings having an improved surface. It is an additional object of the present invention to provide coating compositions which have improved cleanability. It is a final object of the present invention to provide coating compositions which satisfy these requirements without substantially affecting the other valuable properties of the known polyurethane coatings.
Surprisingly, these objectives may be achieved by formulating the two-component coating compositions with the polyisocyanates according to the present invention containing allophanate groups and fluorine which are described hereinafter.